Semiconductor heterojunctions and devices incorporating them are key components of the semiconductor industry. Conventional heterojunctions are formed by epitaxial growth of materials that are lattice matched, or nearly lattice matched, with their growth substrate. Thus, epitaxial growth techniques require that the material being grown take on the same structure and crystalline orientation as the growth substrate. A large lattice mismatch between the materials in successive layers in an epitaxially-grown heterostructure will result in dislocation formation, leading to failed devices.
Wafer bonding is another technique that has been used to fabricate heterostructures of dissimilar materials. However, conventional wafer bonding requires that the bonded surfaces be atomically smooth in order to avoid the formation of voids at the interface and further requires that the materials to be bonded have similar coefficients of thermal expansion in order to render them compatible with the high temperatures used during the bonding process. Moreover, an interface layer formed between two dissimilar materials by wafer bonding is typically characterized by defects and damaged atomic lattices of the bonded materials, as a result of chemical interactions. As a result, such heterostructures find limited use.
Unfortunately, these drawbacks of epitaxial growth and wafer bonding techniques have limited the number of material combinations that can be incorporated into semiconductor heterojunction structures.